Vehicle hub units (e.g. truck hub units) cannot be designed very widely due to manufacturing constraints. For example, an outboard roller set for an outboard roller bearing may be arranged very closely to an inboard roller set for an inboard roller bearing. Due to the inboard roller set and the outboard roller set being designed of the same size, and very closely to each other, the outboard roller bearing (outboard row bearing) may need to be designed to be very large, which may increase overall bearing cost. Furthermore, due to the vehicle hub unit (e.g. a truck hub unit) having the same roller set design for the inboard row of inboard roller bearings and the outboard row of outboard roller bearings, one row (e.g. the inboard roller bearing) may be fully loaded, whereas the other row (e.g. the outboard roller bearing) is not fully loaded (e.g. it is not used to 100% of its loading rate). DE102006017162A1 describes a roller bearing system having structurally identical tapered roller bearings. U.S. Pat. No. 6,149,244 describes a pre-set bearing system which is not a closed system and which may have reliability issues.